Receiver input transformer and method of making the same



Nov. 8, 1960 v. M HEAZEL, JR ETAL 2,958,930

RECEIVER INPUT TRANSFORMER AND METHOD OF MAKING THE SAME Filed June 12,1956 FIG. 2

L1 lLL FIG. 3

INVENTORS ZE'L, JR. H. KUMM ATTORNEYS VINCENT M. HEA

P L H W United States Patent Office RECEIVER INPUT TRANSFORMER ANDMETHOD OF MAKING THE SAME Vincent M. Heazel, Jr., Glen Burnie, andWilliam H.

Kumm, Baltimore, Md., assignors, by mesne assignments, to the UnitedStates of America as represented by the Secretary of the Navy Filed June12, 1956, Ser. No. 591,003 4 Claims. (Cl. 29-15558) This inventionrelates to improvements in transformers and in the method ofmanufacturing transformers.

Although, relatively simple in appearance, the trans former unit is avery complex electrical unit. One of many possible uses of thetransformer in the past has been as a receiver input transformer. Togive the receiver a good noise figure, this type of transformer unitmust resonate with the input and output capacities at the intermediatefrequency, have a definite impedance matching function, and have a verywide bandpass charactcristic. To accomplish these functions, thetransformer must have definite primary and secondary inductances and aclosely held coefiicient of coupling. A required inductance can beestablished by proper winding characteristics, but previously thecoeiiicient of coupling has depended on the proper mechanical tolerancesof the individual pieces of the transformer unit and the placement ofthe primary and secondary windings on this unit. Thus, the electricalcharacteristics of the transformer depended on extremely closemechanical tolerances; consequently, in the past production oftransformers, the manufacturing rejection rate has been extremely high,even as high as eighty percent. The high manufacturing rejection rate isdirectly responsible for a higher production cost.

In accordance with the present invention, the disadvantages stated arenow overcome. There is provided a transformer unit that can bemanufactured without extremely close mechanical tolerances and yet doesnot sacrifice the accuracy of the electrical characteristics, such asthe coefficient of coupling. This is accomplished by manufacturing atransformer unit having two indi- 'vidual pieces wound with the primaryand secondary windings of the transformer. The transformer piece havingthe primary winding wound thereon is adapted to be moved relative to thetransformer piece having the secondary winding wound thereon. Byadjusting the distance one winding is inserted into the other winding, arequired coefficient of coupling for the transformer unit can bederived. This can be accurately set by the use of a Q measuringinstrument. After the required ooeflicient of coupling for thetransformer is set by means of a Q" measuring instrument or any otherequivalent means, the primary winding carrier is cemented to thesecondary winding carrier.

Thus, the present invention contemplates a method of manufacture of atransformer where the electrical characteristics of the transformer,such as the coefiicient of coupling, does not depend on extremely closemechanical tolerances, as required by past methods.

One of the principal objects of this invention is to provide a method ofmanufacture of transformers which lowers the manufacturing rejectionrate.

Another object of the invention is to provide a method of manufacture oftransformers wherein closer electrical tolerances can be obtained,without resorting to close mechanical tolerances.

A further object of the invention is the provision of 2,958,930 PatentedNov. 8, 1960 a cheaper, more accurate and simplified method ofmanufacturing transformers.

Yet another object of the invention is to provide a method for themanufacture of transformers of varied mechanical configurations.

A final object of the present invention is to provide a transformerwhich may be easily and cheaply manufactured.

Other objects and many of the attendant advantages of this inventionwill be readily appreciated as the same becomes better understood byreference to the following detailed description when considered inconnection with the accompanying drawings wherein:

Fig. 1 shows an exploded perspective view, of a preferred embodiment ofthe invention with the primary and secondary windings omitted forpurposes of clarity.

Fig. 2 illustrates a side elevation of a tubular member, partly insection, having a coil wound thereon.

Fig. 3 shows a side elevation of a stud member, partly in section havinga coil Wound thereon.

Fig. 4 is a left-hand end view of the stud member shown in Fig. 3.

Fig. 5 is a right-hand end view of the stud member shown in Fig. 3.

Fig. 6 is an elevation, partly in section of another embodiment of theinvention.

Referring now to the drawings, wherein like reference charactersdesignate like or corresponding parts throughout the several views,there is shown in Fig. l the tubular member 11 adapted to receive thecylindrical stud 12. The tubular member 11 has an elongated body 13,radial spaced flanges 14 and 15, preferably integral with said body 13and spaced from the ends of said body 13. The two flanges 14 and 15define a central portion 17 of the body 13, which is adapted to receivethe coil 24. The coil leads 25 and 26, see Fig. 2, are brought outthrough the holes 18 in flanges 14 and 15. The inner surface 19 of thetubular body 13 is provided with screw threads that are adapted to matewith the screw threads provided on the stud 12. The tubular member 11 ismade of any suitable electric insulating material, such as plastic,rubber or the like, although other electric insulating materials may beused.

The stud 12 is also made of any suitable electric insulating material.The stud 12 is provided with screw threads 22 on its periphery. Thescrew threads 22 are interrupted by a recess or cut-away section 23,thus forming two screw threaded sections 30 and 31; recess 23 is adaptedto receive a coil 34. Elongated grooves 28 and 29 positioned apart, arecut through the threads 22 of section 30 and 31 to provide lead outpaths for the leads 35 and 36 'of the coil 34 (see Fig. 3). A hole 38 isprovided along the longitudinal axis of the stud :12, and may be used asanother path for the leads 35 and 36. A slot 39 for receiving ascrew-driver or the like is provided in one end of the stud 12. In theother end of the stud 12, relatively small pin holes 41 are provided toreceive coupling pins 42, one of which is shown in Figs. 3 and 5.

In assembling the present invention, the stud 12 is screwed into thetubular member 11 to give a required coeflicient of coupling which ismeasured by a Q measuring instrument or the like. When the requiredcoefiicient of coupling is obtained, the stud 12 is cemented into placewithin the tubular member 11. Any other suitable means may be employedto secure the stud 12 within the tubular member 11. Thus, a transformerwith a required coefficient of coupling is obtained without the highmanufacturing rejection rate resulting from extremely close mechanicaltolerances. It is to be noted that the above described method may beused with other than transformers having screw threaded parts as abovedescribed;

however, the screw threaded transformer is perhaps best suited to thismethod. a

The stud 12 may be used as a single member or by the addition of pins42. in holes 41, an additional stud 12 may be mechanically coupled tothe first stud 112. Thus, two studs 12 having coils wound thereon may beadjusted as a single unit relative to the tubular member 11 having acoil wound thereon.

The assembled transformer described above may be manufactured by othermethods than have been described herein. The obvious and most commonlyused method in the past is to assemble the two coils relative to oneanother, rigidly secure the coils to prevent further movement betweenthe coils and then test the assembled transformer to determine if thetransformer has the required coefficient of coupling. This method hasresulted in a very high manufacturing rejection rate, as above noted.Therefore, by using the disclosed method of manufacturing transformers,the disadvantages of the method used in the past can be overcome.

A further embodiment of the present invention is shown in Fig. 6 where atubular member 51, very similar to the member 11, is provided with twocentral portions 57 corresponding to portion 17 of Fig. 1. The radial,spaced flanges53, 54 and 55, correspond to flanges 14 and 15, and alsohave holes 58 therefn. Separate coils are wound on the central portions57 and the leads of said coils are brought out through the holes The twostuds 52 are identical with the stud 12. This embodiment enables theseparate adjusting of the coils-on members 52 in relation to the coilson member 51. By this means, closer electrical characteristics, such asthe coefficient of coupling, may be obtained without regard to extremelyclose mechanical tolerances required in the manufacture of transformersin the past.

Obviously many modifications and variations of the present invention arepossible in the light bf the above teachings. It is therefore to beunderstood that within the scope of the appended claims, the Inventionmay be practiced otherwise than as specifically described.

What is claimed is:

1. The method of manufacturing a transformer comprising providing afirst tubular support with spaced-apart flanges, providing a cylindricalstud member having a reduced diameter over a portIon thereof, placing afirst coil on the tubular support between the spaced-apart flanges,placing a second coil on said cylindrical stud member around the portionof reduced diameter, positioning the cylindrical stud member withinthe'tubular member so that their longitudinal axes coinc'de, connectinga Q measuring means to said coils, adjusting said coils relative to oneanother along their longitudinal axes to obtain a desired coefficient ofcoupling, and then rigidly securfng the coils from further movement withrespect to each other.

2. The method of manufacturing a transformer comprising providing atubular support with spaced-apart flanges thereon, providing acylindrical stud member having a reduced diameter over a portion thereofand diametrically opposite slots in the periphery of the stud memberrunning longitudinally the length of the stud, placing a first coil onthe tubular support between the spaced-apart flanges, placing a secondcoil on the cylindrical stud member around the portion of reduceddiameter, placing the lead-in wires to the second coil in thelongitudinal slots in the stud member to provide an external connectionto the second coil, assembling the transformer by inserting the studmemberiinto the tubular support so that their longitudinal axes'areparallel, connecting a Q measuring instrument to said coils, adjustingsaid coils relative to one another along their longitudinal axes toobtain a desired coeificient of coupling and rigidly securing thecylindrical stud member in place within the tubular support.

3. The method of manufacturing a transformer comprising providing aninternally threaded tubular member" of electric insulating materialhaving spaced-apart flanges.

thereon, providing an externally threaded cylindrical stud member ofelectric insulating material having a reduced diameter over a portionthereof, providing diametrically opposite slots in the external threadsof the stud member 1 running longitudinally the length of the stud,placing a first coil on said tubular member between the spaced-apartflanges and a second coil on said stud member around the reduceddiameter portion, providing holes in the flanges on the tubular memberfor lead-in wires to the first coil, placing the lead-in wires to thesecond coil in the longitudinal slots in the stud member to provide anexternal connection to the second coil, assembling the transformer byscrewing the stud member into the tubular member so that theirlongitudinal axes are parallel, connecting a Q measuring means to thetransformer, accurately setting the transformer to the requiredcoefficient of coupling as determined by said means by screwing the studmember into or out of the tubular member so that the second coil moveslongitudinally with respect to the first coil, and rigidly securing thestud member in place after the required coefficient of coupling has beenobtained.

4. The method of manufacturing a transformer as set forth in claim 3,wherein the step of rigidly securing the stud member in place after therequired coefficient of coupling has been obtained comprises cementingthe stud member in place.

References Cited in the file of this patent UNITED STATES PATENTS1,606,755 Field Nov. 16, 1926 2,055,175 Franz Sept. 22, 1936 2,334,178Dodge Nov. 16, 1943 2,475,829 Fennema July 12, 1949 2,584,723 MackeyFeb. 5, 1952 2,696,659 McCarty Dec. 14, 1954 2,872,723 Levine et al Feb.10, 1959 FOREIGN PATENTS 400,693 Great Britain Nov. 2, 1933 468,380Canada Sept. 26, 1950

